The present invention relates to a method of and an apparatus for manufacturing a vehicle wheel. More specifically, the present invention relates to a process and apparatus for securing a spider to a wheel rim. A "spider" can be defined as the beauty face of an auto wheel inside the wheel rim, or as the center dish or hub of a truck or vehicle wheel.
Vehicle wheels have usually been produced in one piece by methods such as casting or forging. They have also been produced in two or three pieces wherein either a one or a two piece rim is joined with a one piece spider by welding, bolting or riveting. However, all of these known processes are time consuming and fairly expensive. Welding is disadvantageous because it results in a reduced material condition in the heat-affected zone. Bolting or riveting is disadvantageous because non-uniform stress distributions are introduced at the annular joint between the wheel rim and the spider.
Manufacturers have, therefore, begun casting vehicle wheel spiders and forming the rim by spinning the rim from the spider to make a one piece wheel. But this process is time consuming and expensive. In addition, cast wheels have problems in use. Since they are relatively porous, they have a tendency to leak air when a tire without an innertube is mounted thereon. Also, they are not as shiny as the owners of vehicles desire their wheels to be. The industry is currently producing mostly one piece cast rims and two piece rims with a cast spider welded to a rim section formed by methods other than casting. In light of the problems with the conventional vehicle wheel manufacturing methods mentioned above, a need exists for better manufacturing processes for wheels.
There are several known special forming methods which are commonly referred to as high energy rate forming processes. These processes might be more accurately termed high velocity forming techniques. Such processes include explosive forming, electrohydraulic forming, electromagnetic forming and high velocity forging. Related high velocity forming techniques include stress peen forming and ultrasonic activated forming. These processes impart, through the application of high rates of energy transfer, a high velocity to and a high rate of strain to the material being formed. The forming velocity imparted to the material is generally equal to or greater than 10 m/second. The exact means used to achieve this high rate of energy transfer varies from process to process. The effect for most of these processes is, however, the same. The velocity component of the forming operation becomes very large and, in sheet metal forming, improved formability and closer tolerances can result. Chemical energy provided in the form of explosives, propellants or gas mixtures is used in the group of processes known as explosive forming. Large stores of electrical energy, released through high voltage capacitor discharge, are used in both electrohydraulic and electromagnetic forming. Mechanical energy is applied via compressed gas and high velocity hammers to perform operations such as high velocity forging and peen forming.
High energy rate forming processes are described in chapter 19 of volume 2 of the Tool and Manufacturing Engineers' Handbook, Fourth Edition published by the Society of Manufacturing Engineers. Volume 2 is entitled "Forming" and chapter 19 thereof is entitled "Special Forming Methods."
Because of the disadvantages listed previously in connection with the conventional methods of assembling vehicle wheels, such as welding, bolting, riveting, forging and casting, consideration has been given to some of the high energy rate forming processes as the method of manufacturing vehicle wheels.
It is known to apply the electromagnetic forming or magnaforming process in the manufacture of vehicle wheels. One patent disclosing this concept is U.S. Pat. No. 4,334,417 which teaches a wheel blank consisting of a circular flange surrounded by a split rim. The flange is placed between a pair of dies and the split rim is exposed around the periphery of the die. The dies together have an external face reproducing the profile of the intended wheel rim. When magnaforming is applied, the split rim is forced against the die external face in order to produce the rim of the wheel.
Another known process of manufacturing wheels which includes the step of magnaforming is disclosed in U.S. Pat. No. 4,592,121. In this process, a spider is secured to a wheel rim via conventional techniques and, after a tire is positioned on the rim, a final flange of the rim is formed by electromagnetic forming techniques.
However, neither of these known techniques has found wide commercial acceptance. Also, neither is useful in securing a spider to a wheel rim.
Accordingly, it has been considered desirable to develop a new and improved method of manufacturing a wheel and an apparatus therefor which would overcome the foregoing difficulties and others while providing better and more advantageous overall results.